Technical Field
This disclosure relates generally to integrated circuit packaging, and more specifically to preventing artifacts due to underfill in a flip chip imager assembly.
Description of the Related Art
Various devices including but not limited to personal computer systems, desktop computer systems, laptop and notebook computers, tablet or pad devices, digital cameras, digital video recorders, and mobile phones or smart phones may include software and/or hardware that may implement image capture using an image sensor (e.g., one that includes an array of pixel sensors) and an image processor. For example, a device may include an apparatus (e.g., an integrated circuit (IC), such as a system-on-a-chip (SOC), or a subsystem of an IC), that includes an image sensor that collects image information using one or more photodetectors and/or an image processor that processes the collected image information for transmission, display, manipulation, and/or storage.
Flip chip (FC) packaging is commonly used in complementary metal-oxide-semiconductor (CMOS) image sensor (CIS) devices in which the active pixel arrays are mounted faced-down on a printed circuit board (PCB) using a solder alloy, gold-to-gold interconnect, or copper pillars. A composite underfill (UF) material is typically used to reinforce the interconnection for mechanical and drop protection. Flip chip (FC) packaging has been used in packaging backside-illuminated (BSI) image sensors and frontside-illuminated (FSI) image sensors.